MS5561C Micro Altimeter

Transcription

1 SPECIFICATIONS mbar / kpa absolute pressure range High accuracy temperature measurement Integrated miniature pressure sensor 4.75 x 4.25 mm Thin design of 1.6 mm Piezoresistive silicon micromachined sensor 6 coefficients for software compensation stored on-chip 16 Bit ADC, sigma delta converter 3-wire serial interface 1 system clock line ( khz) Low voltage and low power consumption The is a SMD-hybrid device including a precision piezo-resistive pressure sensor and an ADC-Interface IC. It uses a three-wire serial interface for communication. The module dimensions of 4.75 mm x 4.25 mm and a height of only 1.6 mm allows for up-to-date SMD design. It provides a 16 bit data word from a pressure and temperature dependent voltage. The is a low power, low voltage device with automatic power down (ON/OFF) switching. A 3-wire interface is used for all communications with a micro-controller. SENSOR SOLUTIONS /// Page 1 06/2017

2 FEATURES Pressure resolution 0.1 mbar Operating temperature -40 C to +85 C Supply voltage 2.2 V to 3.6 V Low supply current, typ. 4 µa Standby current < 0.1 µa Calibrated temperature and pressure sensor for 2 nd order compensation ESD protected, HBM 4 kv APPLICATIONS Mobile phones GPS receivers Altimeter applications Personal Navigation Devices (PND) Digital cameras with altimeter function BLOCK DIAGRAM VDD Input MUX MCLK SENSOR +IN -IN ADC dig. Filter Digital Interface DIN DOUT SCLK SGND Sensor Interface IC Memory (PROM) 64 bits GND Fig. 1: Block diagram SENSOR SOLUTIONS /// 06/2017 Page 2

3 PIN CONFIGURATION Fig. 2: Pin configuration of Pin Name Pin Type Function SCLK 1 I Serial data clock GND 2 G Ground PV (1) 3 N Negative programming voltage PEN (1) 4 I Programming enable VDD 5 P Positive supply voltage MCLK 6 I Master clock ( khz) DIN 7 I Serial data input DOUT 8 O Serial data output NOTE 1) Pin 3 (PV) and Pin 4 (PEN) are only used by the manufacturer for calibration purposes and should not be connected. ABSOLUTE MAXIMUM RATINGS Parameter Symbol Conditions Min Max Unit Notes Supply voltage VDD Ta = 25 C V Storage temperature TS C 1 Overpressure P Ta = 25 C 5 bar NOTE 1) Storage and operation in an environment of dry and non-corrosive gases. SENSOR SOLUTIONS /// 06/2017 Page 3

4 RECOMMENDED OPERATING CONDITIONS (Ta = 25 C, VDD = 3.0 V unless noted otherwise) Parameter Symbol Conditions Min Typ Max Unit Operating pressure range p mbar abs. Supply voltage VDD V Supply current, VDD = 3.0 V average (1) during conversion (2) Iavg Isc 4 1 µa ma standby (no conversion) Iss 0.1 µa Current consumption into MCLK (3) MCLK = khz 0.5 µa Operating temperature range T C Conversion time tconv MCLK = khz 35 ms External clock signal (4) MCLK khz Duty cycle of MCLK 40/60 50/50 60/40 % Serial data clock SCLK 500 khz NOTES 1) Under the assumption of one conversion every second. Conversion means either a pressure or a temperature measurement started by a command to the serial interface of. 2) During conversion the sensor will be switched on and off in order to reduce power consumption; the total on time within a conversion is about 2 ms. 3) This value can be reduced by switching off MCLK while is in standby mode. 4) It is strongly recommended that a crystal oscillator be used because the device is sensitive to clock jitter. A square-wave form of the clock signal is a must. SENSOR SOLUTIONS /// 06/2017 Page 4

5 ELECTRICAL CHARACTERISTICS DIGITAL INPUTS (T = -40 C.. 85 C, VDD = 2.2 V V) Parameter Symbol Conditions Min Typ Max Unit Input High Voltage VIH 80% VDD 100% VDD V Input Low Voltage VIL 0% VDD 20% VDD V Signal Rise Time tr 200 ns Signal Fall Time tf 200 ns DIGITAL OUTPUTS (T = -40 C.. 85 C VDD = 2.2 V V) Parameter Symbol Conditions Min Typ Max Unit Output High Voltage VOH Isource = 0.6 ma 80% VDD 100% VDD V Output Low Voltage VOL Isink = 0.6 ma 0% VDD 20% VDD V Signal Rise Time tr 200 ns Signal Fall Time tf 200 ns AD-CONVERTER (T = -40 C.. 85 C VDD = 2.2 V V) Parameter Symbol Conditions Min Typ Max Unit Resolution 16 Bit Linear Range 4'000 40'000 LSB Conversion Time MCLK = khz 35 ms INL Within linear range LSB SENSOR SOLUTIONS /// 06/2017 Page 5

6 PRESSURE OUTPUT CHARACTERISTICS With the calibration data stored in the interface IC of the, the following characteristics can be achieved: (VDD = 3.0 V unless noted otherwise) Parameter Conditions Min Typ Max Unit Notes Resolution p = mbar Ta = 25 C 0.1 mbar 1 Absolute Pressure Accuracy p = mbar Ta = 25 C mbar 2 Relative Pressure Accuracy p = mbar Ta = 25 C mbar 3 Relative Pressure Error over Temperature T = C p = mbar T = C p = mbar mbar mbar 4 Long-term Stability 12 months -1 mbar 5 Maximum Error over Supply Voltage VDD = V p = const mbar NOTES 1) A stable pressure reading of the given resolution requires taking the average of 2 to 4 subsequent pressure values due to noise of the ADC. 2) Maximum error of pressure reading over the pressure range. 3) Maximum error of pressure reading over the pressure range after offset adjustment at one pressure point. 4) With the second-order temperature compensation as described in Section "FUNCTION". See next section for typical operating curves. 5) The long-term stability is measured with non-soldered devices. TEMPERATURE OUTPUT CHARACTERISTICS This temperature information is not required for most applications, but it is necessary to allow for temperature compensation of the output. (VDD = 3.0 V unless noted otherwise) Parameter Conditions Min Typ Max Unit Notes Resolution C Accuracy T = 20 C C T = C C 1 Maximum Error over Supply Voltage VDD = V C 2 NOTES 1) With the second-order temperature compensation as described in Section "FUNCTION". See next section for typical operating curves. 2) At Ta = 25 C. SENSOR SOLUTIONS /// 06/2017 Page 6

7 TYPICAL PERFORMANCE CURVES ADC-value D1 vs Pressure (typical) ADC-value D1 (LSB) C 25 C 85 C Pressure (mbar) ADC-value D2 vs Temperature (typical) ADC-value D2 (LSB) Temperature ( C) Absolute Pressure Accuracy after Calibration, 2nd order compensation Pressure error (mbar) C 60 C 25 C 0 C -40 C Pressure (mbar) SENSOR SOLUTIONS /// 06/2017 Page 7

8 Temperature Error Accuracy vs temperature (typical) Temperature error ( C) 5 Temperature error (standard calculation) Temperature error (with 2nd order calculation) Temperature ( C) Pressure Error Accuracy vs temperature (typical) Pressure error (mbar) Perror(1000,1st order) Perror(1000,2nd order) Perror(800,1st order) Perror(800,2nd order) Perror(300,1st order) Perror(300,2nd order) Temperature ( C) SENSOR SOLUTIONS /// 06/2017 Page 8

9 Pressure error vs supply voltage (typical) Pressure error (mbar) mbar 800mbar 300mbar Voltage (V) Temperature error vs supply voltage (typical) Temperature error ( C) Voltage (V) SENSOR SOLUTIONS /// 06/2017 Page 9

10 FUNCTION GENERAL The consists of a piezo-resistive sensor and a sensor interface IC. The main function of the is to convert the uncompensated analogue output voltage from the piezo-resistive pressure sensor to a 16-bit digital value, as well as providing a 16-bit digital value for the temperature of the sensor. Measured pressure (16-bit) Measured temperature (16-bit) D1 D2 As the output voltage of a pressure sensor is strongly dependent on temperature and process tolerances, it is necessary to compensate for these effects. This compensation procedure must be performed by software using an external microcontroller. Sensor D1 D2 Word 1..4 Calculation in external microcontroller Pressure Temperature For both pressure and temperature measurement the same ADC is used (sigma delta converter): for the pressure measurement, the differential output voltage from the pressure sensor is converted for the temperature measurement, the sensor bridge resistor is sensed and converted During both measurements the sensor will only be switched on for a very short time in order to reduce power consumption. As both, the bridge bias and the reference voltage for the ADC are derived from VDD, the digital output data is independent of the supply voltage. FACTORY CALIBRATION Every module is individually factory calibrated at two temperatures and two pressures. As a result, 6 coefficients necessary to compensate for process variations and temperature variations are calculated and stored in the 64-bit PROM of each module. These 64-bit (partitioned into four words of 16-bit) must be read by the microcontroller software and used in the program converting D1 and D2 into compensated pressure and temperature values. PRESSURE AND TEMPERATURE MEASUREMENT The sequence of reading pressure and temperature as well as of performing the software compensation is depicted in Fig. 3 and Fig. 5. First Word1 to Word4 have to be read through the serial interface. This can be done once after reset of the microcontroller that interfaces to the. Next, the compensation coefficients C1 to C6 are extracted using bit-wise logical- and shift-operations (refer to Fig. 4 for the bit-pattern of Word1 to Word4). For the pressure measurement, the microcontroller has to read the 16-bit values for pressure (D1) and temperature (D2) via the serial interface in a loop (for instance every second). Then, the compensated pressure is calculated out of D1, D2 and C1 to C6 according to the algorithm in Fig. 3 (possibly using quadratic temperature compensation according to Fig. 5). All calculations can be performed with signed 16-bit variables. Results of multiplications may be up to 32-bit long (+sign). In the flow according to Fig. 3 a division follows each multiplication. This division can be performed by bit-wise shifting (divisors are to the power of 2). It is ensured that the results of these divisions are less than (16 bit). For the timing of signals to read out Word1 to Word4, D1, and D2 please refer to the paragraph Serial Interface". SENSOR SOLUTIONS /// 06/2017 Page 10

11 Start Basic equations: Example: System initialisation Read calibration data (factory calibrated) from PROM of Word1, Word2, Word3 and Word4 (4x16 Bit) Word1 = Word2 = Word3 = Word4 = Convert calibration data into coefficients: (see bit pattern of Word1-Word4) C1: Pressure sensitivity (15 Bit) C2: Pressure offset (12 Bit) C3: Temperature coefficient of pressure sensitivity (10 Bit) C4: Temperature coefficient of pressure offset (10 Bit) C5: Reference Temperature (11 Bit) C6: Temperature coefficient of the temperature (6 Bit) SENST1 OFFT1 TCS TCO T ref TEMPSENS C1 = C2 = 1324 C3 = 737 C4 = 393 C5 = 628 C6 = 25 Pressure and temperature measurement Read digital pressure value from D1 (16 Bit) Read digital temperature value from Calculate calibration temperature UT1 = 8*C Difference between actual temperature and reference temperature: dt = D2 - UT1 Actual temperature: D2 (16 Bit) Calculate actual temperature TEMP = dt*(c6+50)/2 10 (0.1 C resolution) dt(d2) = D2 - T ref TEMP(D2) = 20 +dt(d2)*tempsens D1 = D2 = UT1 = dt = 2608 TEMP = 391 = 39.1 C Calculate temperature compensated pressure Offset at actual temperature: OFF = C2*4 + ((C4-512)*dT)/2 12 Sensitivity at actual temperature: SENS = C1 + (C3*dT)/ X = (SENS * (D1-7168))/ OFF OFF(D2) = OFFT1+TCO*dT(D2) SENS(D2) = SENST1+TCS*dT(D2) OFF = 5220 SENS = X = Temperature compensated pressure: P = X*10/ *10 (0.1 mbar resolution) P(D1,D2) = D1*SENS(D2)-OFF(D2) P = 9716 = mbar Display pressure and temperature value Fig. 3: Flow chart for pressure and temperature reading and software compensation SENSOR SOLUTIONS /// 06/2017 Page 11

12 NOTES 1) Readings of D2 can be done less frequently, but the display will be less stable in this case. 2) For a stable display of 1 mbar resolution, it is recommended to display the average of 8 subsequent pressure values. C1 (15 Bit) C5/I 1 Bit Word1 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB10 C5/II (10 Bit) C6 (6 Bit) Word2 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB5 DB4 DB3 DB2 DB1 DB0 C4 (10 Bit) C2/I (6 Bit) Word3 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB11 DB10 DB9 DB8 DB7 DB6 C3 (10 Bit) C2/II (6-Bit) Word4 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB5 DB4 DB3 DB2 DB1 DB0 Fig. 4: Arrangement (Bit-pattern) of calibration data in Word1 to Word4 SENSOR SOLUTIONS /// 06/2017 Page 12

13 SECOND-ORDER TEMPERATURE COMPENSATION In order to obtain full temperature accuracy over the whole temperature range, it is recommended to compensate for the non-linearity of the output of the temperature sensor. This can be achieved by correcting the calculated temperature and pressure by a second order correction factor. The second-order factors are calculated as follows: TEMP < TEMP 450 TEMP > 450 yes Low Temperatures yes No correction yes High Temperatures T2 = 11*(C6+24)*(200 - TEMP)*(200 TEMP) / 2 20 P2 = 3 *T2 * (P )/2 14 T2 = 0 P2 = 0 T2 = 3*(C6+24)*(450 - TEMP)*(450 TEMP) / 2 20 P2 = T2 * (P )/2 13 Calculate pressure and temperature TEMP = TEMP T2 P = P P2 Fig. 5: Flow chart for calculating the temperature and pressure to the optimum accuracy. SENSOR SOLUTIONS /// 06/2017 Page 13

14 SERIAL INTERFACE The communicates with microprocessors and other digital systems via a 3-wire synchronous serial interface as shown in Fig. 1. The SCLK (Serial clock) signal initiates the communication and synchronizes the data transfer with each bit being sampled by the on the rising edge of SCLK and each bit being sent by the on the rising edge of SCLK. The data should thus be sampled by the microcontroller on the falling edge of SCLK and sent to the with the falling edge of SCLK. The SCLK-signal is generated by the microprocessor s system. The digital data provided by the on the DOUT pin is either the conversion result or the software calibration data. In addition, the signal DOUT (Data out) is also used to indicate the conversion status (conversion-ready signal, see below). The selection of the output data is done by sending the corresponding instruction on the pin DIN (Data input). Following is a list of possible output data instructions: Conversion start for pressure measurement and ADC-data-out D1 (Figure 6a) Conversion start for temperature measurement and ADC-data-out D2 (Figure 6b) Calibration data read-out sequence for Word1 (Figure 6c) Calibration data read-out sequence for Word2 (Figure 6d) Calibration data read-out sequence for Word3 (Figure 6c) Calibration data read-out sequence for Word4 (Figure 6d) RESET sequence (Figure 6e) Every communication starts with an instruction sequence at pin DIN. Fig. 6 shows the timing diagrams for the. The device does not need a Chip select signal. Instead there is a START sequence (3-Bit high) before each SETUP sequence and STOP sequence (3-Bit low) after each SETUP sequence. The SETUP sequence consists in 4-Bit that select a reading of pressure, temperature or calibration data. In case of pressure- (D1) or temperature- (D2) reading the module acknowledges the start of a conversion by a low to high transition at pin DOUT. Two additional clocks at SCLK are required after the acknowledge signal. Then SCLK is to be held low by the microcontroller until a high to low transition on DOUT indicates the end of the conversion. This signal can be used to create an interrupt in the microcontroller. The microcontroller may now read out the 16 bit word by giving another 17 clocks on the SLCK pin. It is possible to interrupt the data READOUT sequence with a hold of the SCLK signal. It is important to always read out the last conversion result before starting a new conversion. The RESET sequence is special as the module in any state recognizes its unique pattern. By consequence, it can be used to restart if synchronization between the microcontroller and the has been lost. This sequence is 21-bit long. The DOUT signal might change during that sequence (see Fig. 6e). It is recommended to send the RESET sequence before each CONVERSION sequence to avoid hanging up the protocol permanently in case of electrical interference. SCLK Conversion start for pressure measurement and ADC-data-out "D1": end of conversion DOUT start of conversion conversion (33ms) ADC-data out MSB ADC-data out LSB DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DIN sequence: START+P-measurement Bit0 Bit1 Bit2 Bit3 Bit4 Start-bit Bit5 Bit6 Bit7 Bit8 Bit9 Setup-bits Stop-bit Fig. 6a: D1 ACQUISITION sequence SENSOR SOLUTIONS /// 06/2017 Page 14

15 SCLK Conversion start for temperature measurement and ADC-data-out "D2": end of conversion DOUT start of conversion conversion (33ms) ADC-data out MSB ADC-data out LSB DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DIN sequence: START+T-measurement Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Start-bit Setup-bits Bit6 Bit7 Bit8 Bit9 Stop-bit Fig. 6b: D2 ACQUISITION sequence SCLK Calibration data read out sequence for word 1/ word 3: DOUT coefficient-data out MSB DB7 DB6 DB5 DB4 DB3 DB2 DB1 coefficient-data out LSB DB0 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DIN Bit0 Bit1 Bit2 sequence: coefficient read + address Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9Bit10Bit11 Start-bit Setup-bits Stop-bit address word 1 address word 3 Fig. 6c: Word1, Word3 READING sequence SCLK Calibration data read out sequence for word 2/ word 4: DOUT coefficient-data out MSB DB7 DB6 DB5 DB4 DB3 DB2 DB1 coefficient-data out LSB DB0 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DIN sequence: coefficient read + address Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Bit10Bit11 Start-bit Setup-bits Stop-bit address word 2 address word 4 Fig. 6d: W2, W4 READING sequence SCLK RESET - sequence: DIN DOUT sequence: RESET Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Bit10Bit11Bit12Bit13Bit14Bit15Bit16Bit17Bit18Bit19Bit20 Fig. 6e: RESET sequence (21 bit) SENSOR SOLUTIONS /// 06/2017 Page 15

16 APPLICATION INFORMATION GENERAL The advantage of combining a pressure sensor with a directly adapted integrated circuit is to save other external components and to achieve very low power consumption. The main application field for this system includes portable devices with battery supply, but its high accuracy and resolution make it also suited for industrial and automotive applications. The possibility to compensate the sensor by software allows the user to adapt it to his particular application. Communication between the and the widely available microcontrollers is realized over an easy-to-use 3-wire serial interface. Customers may select which microcontroller system to be used, and there are no specific standard interface cells required, which may be of interest for specially designed 4 bitmicrocontroller applications. For communication via SPI interface please refer to application note AN510 that may be downloaded from the MEAS Switzerland website. CALIBRATION The is factory calibrated. The calibration data is stored inside the 64 bit PROM memory. SOLDERING Please refer to the application note AN808 for all soldering issues. HUMIDITY, WATER PROTECTION This module is designed for the integration into portable devices and sufficiently protected against humidity. A silicone gel for enhanced protection against humidity covers the membrane of the pressure transducer. The module must not be used for under water applications. LIGHT SENSITIVITY The is protected against sunlight by a layer of white gel. It is, however, important to note that the sensor may still be slightly sensitive to sunlight, especially to infrared light sources. This is due to the strong photo effect of silicon. As the effect is reversible there will be no damage, but the user has to take care that in the final product the sensor cannot be exposed to direct light during operation. DECOUPLING CAPACITOR Particular care must be taken when connecting the device to power supply. A 47 F tantalum capacitor must be placed as close as possible of the 's VDD pin. This capacitor will stabilize the power supply during data conversion and thus, provide the highest possible accuracy. SENSOR SOLUTIONS /// 06/2017 Page 16

17 APPLICATION EXAMPLE: ALTIMETER SYSTEM USING is a circuit that can be used in connection with a microcontroller in mobile altimeter applications. It is designed for low-voltage systems with a supply voltage of 3V, particularly in battery applications. The is optimised for low current consumption as the AD-converter clock (MCLK) can use the khz frequency of a standard watch crystal, which is supplied in most portable watch systems. For applications in altimeter systems MEAS Switzerland can deliver a simple formula to calculate the altitude, based on a linear interpolation, where the number of interpolation points influences the accuracy of the formula. 3V-Battery LCD-Display VDD khz XTAL1 VDD MCLK 47uF Tantal XTAL2 Keypad DIN DOUT SCLK Microcontroller GND GND EEPROM optional Figure 7: Demonstration of in a mobile altimeter RECOMMENDED PAD LAYOUT Pad layout for bottom side of soldered onto printed circuit board. SENSOR SOLUTIONS /// 06/2017 Page 17

18 DEVICE PACKAGE OUTLINES Fig. 8: Device package outlines of MS5561-C SENSOR SOLUTIONS /// 06/2017 Page 18

19 ASSEMBLY MOUNTING The can be placed with automatic Pick&Place equipment using vacuum nozzles. It will not be damaged by the vacuum. Due to the low stress assembly the sensor does not show pressure hysteresis effects. It is important to solder all contact pads to avoid floating of the sensor during soldering. The pins PEN and PV shall be left open or connected to VDD. Do not connect the pins PEN and PV to GND! CLEANING The has been manufactured under cleanroom conditions. Each device has been inspected for the homogeneity and the cleanness of the silicone gel. It is therefore recommended to assemble the sensor under class or better conditions. Should this not be possible, it is recommended to protect the sensor opening during assembly from entering particles and dust. To avoid cleaning of the PCB, solder paste of type no-clean shall be used. Cleaning might damage the sensor! ESD PRECAUTIONS The electrical contacts except programming pads are protected against ESD up to 4 kv HBM (human body model). The is shipped in antistatic transport boxes. Any test adapters or production transport boxes used during the assembly of the sensor shall be of an equivalent antistatic material. SENSOR SOLUTIONS /// 06/2017 Page 19

20 SHIPPING PACKAGE Tape Units per reel Minimum empty leader (right side of drawing) Tape widths 12 mm Minimum empty trailer Tape material Black Conductive Polystyrene (left side of drawing, Reel diameter 13 / 330 mm direction of unreeling) 250 mm 250 mm Fig, 9: Outline of tape for Fig.10: Outline of reel for SENSOR SOLUTIONS /// 06/2017 Page 20

21 ORDERING INFORMATION Product Code Product Art. No Package Comments MS5561-C Small Size SMD with metal lid Module height 1.6 mm NORTH AMERICA Measurement Specialties, Inc., a TE Connectivity company Tel: customercare.frmt@te.com EUROPE Measurement Specialties (Europe), Ltd., a TE Connectivity Company Tel: customercare.bevx@te.com ASIA Measurement Specialties (China) Ltd., a TE Connectivity company Tel: customercare.shzn@te.com TE.com/sensorsolutions Measurement Specialties, Inc., a TE Connectivity company. Measurement Specialties, TE Connectivity, TE Connectivity (logo) and EVERY CONNECTION COUNTS are trademarks. All other logos, products and/or company names referred to herein might be trademarks of their respective owners. The information given herein, including drawings, illustrations and schematics which are intended for illustration purposes only, is believed to be reliable. However, TE Connectivity makes no warranties as to its accuracy or completeness and disclaims any liability in connection with its use. TE Connectivity s obligations shall only be as set forth in TE Connectivity s Standard Terms and Conditions of Sale for this product and in no case will TE Connectivity be liable for any incidental, indirect or consequential damages arising out of the sale, resale, use or misuse of the product. Users of TE Connectivity products should make their own evaluation to determine the suitability of each such product for the specific application TE Connectivity Ltd. family of companies All Rights Reserved. SENSOR SOLUTIONS /// 06/2017 Page 21